"It's tragic for those families and too late by the time we get to it."
Agriculture, forestry, mining and construction were New Zealand's most dangerous industries, Mr Key said.
"The new health and safety laws are coming in and they will put new and more stringent requirements on some businesses - and to a certain degree the rural sector will be affected a bit by that ... we are very conscious on the one hand of not drowning out business with new regulations, but on the other recognising that workplaces need to be safer."
The Government was helping Wairarapa businesses by continuing to review business regulations, he said.
"We have to make sure that they have the infrastructure, broadband, roading, stable electricity networks - all those things - and the second thing is they need access to international markets so that when we go and sign these free trade deals it's not a theoretical thing ... The third thing is we do have to continually look at whether the rules and regulations around business are appropriately set."
The Copthorne lunch was part of the Prime Minister's whistle-stop tour of Wairarapa, which kicked off with a meeting at Juken New Zealand and concluded with a visit to Fonterra.
Those dining with Mr Key included leading Wairarapa businesspeople and all three mayors, who tucked into a dessert of mini-pavlovas, chocolate brownies and miniature tarts, while the Prime Minister spoke about interest rates, oil prices, export markets, education, the Resource Management Act and the Christchurch rebuild.
Mr Key highlighted the strength of New Zealand's "rock-star economy", saying economic growth was robust at about 3.5 per cent. Although dairy prices were weak, forestry prices were strong and manufacturing was returning to New Zealand, Mr Key said.
"Chinese manufacturing is closing down and stuff is coming back to New Zealand."
With countries like Indonesia and India becoming more prosperous, there were great opportunities for exporters, he said.
"The long-term outlook from Asia is huge, and it's not just China.
"When people get wealthy they buy protein ...
"The average Indonesian person consumes 2.1kg of beef per person per year - my son eats that on a Saturday night. The average Kiwi eats 50kg a year.
"So as they get wealthier, they are eating a lot more beef, a lot more dairy and a lot more everything."